Vascular Cognitive Impairment In Rat Model:Study Of Structural Magnetic Resonance Imaging And Diffusion Tensor Imaging In Early Diagnosis

Objective: Using structural magnetic resonance imaging and diffusion tensor imaging to observe the changes of hippocampal volume and microscopic brain white matter in vascular cognitive impairment rat, contrast with pathology,to explore the imaging indexes of early diagnosis of VCI.Methods: A modified 4-VO Pulsinelli method was used to replicate the VCI rat model.30 rats were divided into model group(20 rats) and control group(10 rats).Morris water maze test was used to detect learning and memory abilities of rats;T2WI and DTI imaging scans were performed in all rats at 2 weeks, 1month, 3months, and 5months respectively after surgery.The manual segmentation of region of interest method(ROI)was used to analysis the change of hippocampal volume and FA value on T2 WI and DTI images.The voxel based analysis(VBA)was used to analysis the change of FA value of all brain on DTI images.The rat brain tissue slices were underwent HE staining and Nissl staining to observe the morphological changes.Results: 1.Compared with the control group, the learning and memory ability of rats in VCI model group(2 week, 1 month, 3 months, 5 months) was significantly decreased. The difference is statistically significant(p < 0.05) of learning and memory ability between VCI(2 weeks) and VCI( 1 month, 3 months, 5 months) rats, and VCI(1weeks) and VCI( 3 months, 5 months) rats; the difference is not obvious(p >0.05) of learning and memory ability between VCI(1 month) and VCI(3 months) rats.The escape latency was significant difference between VCI(3 month) and VCI(5months) rats, the difference is statistically significant(p < 0.05), and change of thefirst cross platform time, crossing platform number is not obvious(p > 0.05);2. We use the ROI method found the hippocampal volume and FA value in VCI( 2 weeks, 1month) rats were no significantly change compared with the control group;On the contrary,there were significantly change between VCI( 3 months, 5 months) rats and control group.3. We use the VBA method found in VCI model group, there was no significant reduction(p<0.05)of FA in the brain area after 2 weeks of operation;Postoperative 1 month FA values decreased significantly(p<0.05) in the regions is mainly left thalamus, cingulate, right insular lobe, bilateral frontal cortex,striatum, corpus callosum; with the extension of time, the postoperative 3 months the FA values significantly lower(p<0.05)area mainly for the right hippocampus,frontal cortex, anterior commissure, corpus callosum, thalamus, insula, striatum,olfactory tract; postoperative 5 month the FA values significantly reduced(p<0.05)area is mainly in the bilateral hippocampus, bilateral striatum, frontal lobe, parietal lobe, thalamus, former United, corpus callosum and cingulate.4.Pyramidal cells in the hippocampal showed gradually degeneration and nuclear condensation and cytoplasmic Nissl bodies gradually reduction and disappearance.Conclusion: 1. In this study, we through the T2 WI and DTI images found that VCI rats appear obvious atrophy and FA decread of hippocampal in 3months after operation,suggest that the changes of hippocampal volume and microscopic white matter can be used as an indicator for early diagnosis of VCI.2.Through the whole brain VBA analysis method we found that FA values decreased in VCI rats brain with cognitive impairment.It suggests that the decrease of FA value may be helpful to the early diagnosis and severity evaluation of VCI.